Lecture 1- Introduction + Overview Flashcards
Bacterial physiology
- study of the structures and functions of bacterial cells and their parts
Bacterial structures
Bacterial functions
- how it works
- growth and reproduction
- metabolism
- motility
- interactions with host and environment
Overview of a bacterial cell
Capsule
- slime layer or glycocalyx
- made up of carbohydrates
EXCEPTION
- Bacillus anthracis = made up of polypeptides
Functions of the capsule
- Mediates adherence/attachment to things
- Makes up the biolfilm matrix
- Protects from phagocytosis by WBCs
- Refractory to antibiotics
- Resists drying
- Nutrient reservoir
Flagella / flagellum
- aka H antigen
- long, threadlike structures made up of protein
- major function of motility
- made up of three parts: basal body, hook, filament
Monotrichous
single polar flagellum
Lophotrichous
cluster of polar flagella
Amphitrichous
flagella at both poles
either single or in clusers
Perithrichous
cell encircled by lateral flagella
Pili / fimbriae
- fine + hair like structures made up of proteins
Somatic pili
- mediate adherence and biofilm formation
Sex / f pili
- mediate conjugation (transfer of dna via contact)
- some are receptors for bacteriophages
cell wall
- provides rigidity / maintains cell shape
- is a barrier to hazardous things entering the cell
gram positive cell wall
- single, uniform and thick layer of peptidoglycan
- 15-80 nm
gram negative cell wall
- 2 layers
- thin peptidoglycan and an outermembrane
cell wall of mycobacteria
- layer of mycolic acids and arabinogalactan + peptidoglycan
mycoplasma cell wall
doesnt exist
peptidoglycan
- repeating units of NAG and NAM forming the glycan chains
- glycan chains cross-linked by peptides
- NAG= N-acetylglucosamine
- NAM= N-acetylmuramic acid
Penicillins
inhibit the crosslinking of glycan chains in peptidoglycan
Things unique to Gram +
- Teichoic acids and lipoteichoic acids
- linear polymers of glycerol phosphastes or ribitol phosphates
- provides negative charges and hydrophobic sites for adherence
Teichoic acids
- covalently linked to peptidoglycan
lipoteichoic acid
- contains fatty acid chains allowing the molecules to anchor to the cell membrane
lipopolysaccharides (LPS)
- only in gram negative bacteria
- outer leaflet of the outer membrane
- made of 3 parts:
- lipid A
- core polysaccharide
- O-antigen (polysaccharide)
- endotoxin
- effects: inflammation, shock
- can be “smooth” or “rough”
gram negative bacteria
- LPS
porins
- “gateways” for small hydrophilic molecules to enter the cell
Major differences between G+ and G- bacteria
Gram positive
- thick peptidoglycan
- teichoic acid and lipoteichoic acid
Gram negative
- thin peptidoglycan
- outer membrane
- LPS
- has a periplasm: the space between the outer membrane and cytoplasmic membrane
cytoplasmic /inner membrane
- phospholipid bilayer with proteins
- the ultimate barrier to hostile agents
- site of electron transport chain
proton motive force
- used by bacteria to do useful works: ATP synthesis, rotate flagella, solute transport
Cytoplasm
- DNA, RNA, ribosomes, proteins, ions
- inlusion body: poly-B-hydroxybutyrate can be processed into biodegradable plastic bags
- endospore
- membrane invaginations (ex: photosynthetic structure)
- gas vacuoules
Extracellular products
- toxins, enzymes, acids, solvents, antibiotics
Harmful
- tetanus toxin: causes tetanus
- collagenase: degrades collagen, help bacteria to spread an infection
- lactic acid: causes dental caries
Beneficial
- enzymes: amylase, breakdowns starch
- acetic acid: vinegar
- ethanol (solvent): fuel
- antibiotics: polymyxin and tetracycline
